Research On Synchronization Of MIMO-OFDM System Based On LTE Specification

At present, OFDM and MIMO have been adopted by IEEE 802.11a, 802.16e, and the 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) system. From the present study, OFDM/OFDMA, it seems that MIMO technologies will become mainstream technologies for 4th Generation (4G). However, the cell search including time and frequency synchronization, and cell ID identification is one of the most important issue that must be deal with for any OFDM cellular systems.This paper focuses on two hot topics: timing and carrier synchronization for distributed MIMO-OFDM system with multi-time delay and multi-frequency offset; and cell initial search for LTE system. In the study of time and frequency synchronization for distributed MIMO-OFDM system, in order to solve the problem of timing perfermace deterioration of the existing algorithm in multipath-fading channel, two improved symbol timing synchronization algorithms based on unequal period and reverse conjugate symmetric synchronization pattern are proposed, and the simulation results show that the proposed method offers an accurate estimation; and then a multi-frequency offset estimation algorithm is presented, simulation results show its good estimation performance under various channel environments. In the study of cell search for LTE system, in order to overcome the drawbacks of correlation peak illegibility of the traditional ML algorithm, and frequency offset sensitivity of the algorithm using the full correlation of the Zadoff-Chu sequence, an improved timing synchronization algorithm using the partial correlation of the ZC sequence and MIMO maximum ration combining is proposed, which achieve excellent performance compared with current algorithms. Furthermore, centrosymmetric characteristic of LTE Primary-SCH in frequency domain is investigated; utilizing this property a novel integer carrier frequency offset (CFO) estimation method is proposed, which is robust under multi-path fading channels and can be implemented easily. Finally, taking the practical physical layer transmission control mechanism into account, a solution is proposed to the whole architecture for the cell initial search in a LTE system receiver.